1. Field of the Invention
This invention relates to purification of air or gas and more particularly refers to a new and improved method and apparatus for the selective adsorption of individual vaporous or gaseous impurities from air or other gases.
2. Description of the Prior Art
One problem of gas purification technology, especially of air purification technology, is the separation of vaporous or gaseous impurities from a stream of gas. It is known to solve such problems by means of adsorption techniques. It is likewise known to utilize adsorption filters for this purpose. It is also known to accomplish the separation of such impurities by thermal combustion which may take place in the flame, as well as by means of a catalyst. It is also known to store adsorbable impurities in an adsorption filter and to recover them after desorption, for instance through condensation, or to burn them after the necessary combustion air has been added. A disadvantage of these methods is that there is no selective effect and thus, mixtures of vapors or gaseous impurities can be precipitated but not selectively separated. The problem of separation is concerned with practical applications as for example in painting technology. Separating the paint solvents used is not only a necessity with respect to keeping the air clean but the recovery subsequent to the separation can result in substantial economic advantages if these recovered solvents can be reintroduced into the painting process at low cost. In the exhaust air of painting lines, there are, in addition to solvents, also softeners with a higher boiling point than the solvents. The recovery of the softener or plasticizer can as a rule be dispensed with. Recovery of the softeners is generally uneconomical and may cause contamination of the solvents sought to be recovered.